Using your sleeve ain´t a very good idea, since it may contain small parts of material which may create scratches and marks on the screen. Yes, the iPad and iPhone screens are remarkable since it's almost impossible to damage them - but it's still possible. So make sure your sleeve is a 100% clean if you tend to use it for cleaning purposes!
Otherwise, there are "cleaning kits" sold in every applestore, aswell as in almost every major electronics store. They doesn't cost more than a few bucks, and contain a bottle of cleaning fluid and a microfiber cloth. That's all you'll ever need for a perfect result - guaranteed!